Envelope tracking circuit and related power amplifier apparatus

ABSTRACT

An envelope tracking (ET) circuit and related power amplifier apparatus is provided. An ET power amplifier apparatus includes an ET circuit and a number of amplifier circuits. The ET circuit is configured to provide a number of ET modulated voltages to the amplifier circuits for amplifying concurrently a number of radio frequency (RF) signals. The ET circuit includes a target voltage circuit for generating a number of ET target voltages adapted to respective power levels of the RF signals and/or respective impedances seen by the amplifier circuits, a supply voltage circuit for generating a number of constant voltages, and an ET voltage circuit for generating the ET modulated voltages based on the ET target voltages and a selected one of the constant voltages. By employing a single ET circuit, it may be possible to reduce the footprint and improve heat dissipation of the ET power amplifier apparatus.

RELATED APPLICATIONS

This application claims the benefit of provisional patent applicationSer. No. 62/726,572, filed Sep. 4, 2018, the disclosure of which ishereby incorporated herein by reference in its entirety.

This application is related to U.S. patent application Ser. No.16/250,229, filed Jan. 17, 2019, now U.S. Pat. No. 10,951,175, entitled“ENVELOPE TRACKING CIRCUIT AND RELATED POWER AMPLIFIER APPARATUS,” thedisclosure of which is hereby incorporated herein by reference in itsentirety.

FIELD OF THE DISCLOSURE

The technology of the disclosure relates generally to an envelopetracking (ET) power amplifier apparatus and an ET circuit therein.

BACKGROUND

Mobile communication devices have become increasingly common in currentsociety for providing wireless communication services. The prevalence ofthese mobile communication devices is driven in part by the manyfunctions that are now enabled on such devices. Increased processingcapabilities in such devices means that mobile communication deviceshave evolved from being pure communication tools into sophisticatedmobile multimedia centers that enable enhanced user experiences.

The redefined user experience requires higher data rates offered bywireless communication technologies, such as fifth-generation new-radio(5G-NR) technology configured to communicate a millimeter wave (mmWave)radio frequency (RF) signal(s) in an mmWave spectrum located above 12GHz frequency. To achieve the higher data rates, a mobile communicationdevice may employ a power amplifier(s) to increase output power of themmWave RF signal(s) (e.g., maintaining sufficient energy per bit).However, the increased output power of mmWave RF signal(s) can lead toincreased power consumption and thermal dissipation in the mobilecommunication device, thus compromising overall performance and userexperiences.

Envelope tracking (ET) is a power management technology designed toimprove efficiency levels of the power amplifier(s) to help reduce powerconsumption and thermal dissipation in the mobile communication device.As the name suggests, an ET circuit(s) can be configured to keep trackof a time-variant power envelope(s) of the mmWave RF signal(s)communicated by the mobile communication device. As such, the ETcircuit(s) can constantly adjusts a voltage(s) supplied to the poweramplifier(s) based on instantaneous power level of the mmWave RFsignal(s) to improve linearity and efficiency of the power amplifier(s).

Notably, the mmWave RF signal(s) can be susceptible to attenuation andinterference resulting from various sources. As such, the mobilecommunication device may employ multiple transmitters/antennas tosimultaneously transmit a number of mmWave RF signals via a techniqueknown as RF beamforming. Given that the mmWave RF signals may beassociated with different time-variant power envelopes, it may benecessary to multiple power amplifiers for amplifying simultaneously themultiple mmWave RF signals. Accordingly, it may also be necessary toemploy multiple ET circuits to supply simultaneously multiple voltagesto the multiple power amplifiers. As a result, the mobile communicationdevice may require a larger footprint for accommodating the multiple ETcircuits. Furthermore, the increased number of ET circuits may also leadto increased complexity and heat dissipation in the mobile communicationdevice. Hence, it may be desired to support RF beamforming in the mobilecommunication device without increasing number of the ET circuits.

SUMMARY

Embodiments of the disclosure relate to an envelope tracking (ET)circuit and related power amplifier apparatus. In one aspect, an ETpower amplifier apparatus includes an ET circuit and a number ofamplifier circuits. The ET circuit is configured to provide a number ofET modulated voltages to the amplifier circuits for amplifyingconcurrently a number of radio frequency (RF) signals to respectivepower levels. In another aspect, the ET circuit is configured to includea target voltage circuit, a supply voltage circuit, and an ET voltagecircuit. The target voltage circuit is configured to generate a numberof ET target voltages adapted to the respective power levels of the RFsignals and/or respective impedances seen by the amplifier circuits. Thesupply voltage circuit is configured to generate a number of constantvoltages. The ET voltage circuit is configured to generate the ETmodulated voltages based on the ET target voltages and a selected one ofthe constant voltages. As such, it may be possible to adapt the ETmodulated voltages to the respective power levels of the RF signalsand/or respective impedances seen by the amplifier circuits, thushelping to improve linearity and efficiency of the amplifier circuits.Further, by providing the ET modulated voltages from a single ETcircuit, it may be possible to reduce the footprint and improve heatdissipation of the ET power amplifier apparatus.

In one aspect, an ET voltage circuit is provided. The ET voltage circuitincludes a number of voltage selection circuits each configured toreceive a number of constant voltages. The ET voltage circuit alsoincludes a number of voltage controllers coupled to the voltageselection circuits, respectively. The voltage controllers are configuredto receive a number of ET target voltages, respectively. The voltagecontrollers are also configured to control the voltage selectioncircuits to output a number of selected constant voltages based on theET target voltages, respectively. The voltage controllers are alsoconfigured to cause a number of ET modulated voltages to be generatedbased on the ET target voltages and the selected constant voltages,respectively.

In another aspect, a target voltage circuit is provided. The targetvoltage circuit is configured to receive a reference target voltagecorresponding to a dynamic voltage range. The target voltage circuit isalso configured to offset the reference target voltage to a baselinereference voltage corresponding to the dynamic voltage range. The targetvoltage circuit is also configured to determine a number of slopefactors. The target voltage circuit is also configured to multiply theslope factors with the dynamic voltage range to generate a number of ETtarget voltages, respectively. The target voltage circuit is alsoconfigured to adjust the ET target voltages based on a number of offsetfactors, respectively.

In another aspect, a supply voltage circuit is provided. The supplyvoltage circuit includes an inductor-based voltage circuit configured togenerate a direct current (DC) voltage based on a battery voltage. Thesupply voltage circuit also includes a number of output ports configuredto output a number of constant voltages, respectively. A first selectedoutput port among the output ports is coupled to the inductor-basedvoltage circuit to output the DC voltage as a first selected constantvoltage among the constant voltages. One or more second selected outputports among the output ports are configured to output one or more secondselected constant voltages among the constant voltages different fromthe first selected constant voltage. The supply voltage circuit alsoincludes a capacitor-based voltage circuit coupled to the inductor-basedvoltage circuit. The capacitor-based voltage circuit is configured togenerate the one or more second selected constant voltages at the one ormore second selected output ports, respectively. The supply voltagecircuit also includes a controller. The controller is configured toreceive a feedback signal indicative of a preselected constant voltageamong the constant voltages. The controller is also configured tocontrol the inductor-based voltage circuit to adjust the DC voltagebased on the preselected constant voltage.

Those skilled in the art will appreciate the scope of the presentdisclosure and realize additional aspects thereof after reading thefollowing detailed description of the preferred embodiments inassociation with the accompanying drawing figures.

BRIEF DESCRIPTION OF THE DRAWING FIGURES

The accompanying drawing figures incorporated in and forming a part ofthis specification illustrate several aspects of the disclosure, andtogether with the description serve to explain the principles of thedisclosure.

FIG. 1 is a schematic diagram of an exemplary envelope tracking (ET)power amplifier apparatus configured according to an embodiment of thepresent disclosure to support a number of amplifier circuits based on asingle ET circuit;

FIG. 2 is a schematic diagram providing an exemplary illustration of atarget voltage circuit in the ET circuit of FIG. 1 configured accordingto an embodiment of the present disclosure to generate a number of ETtarget voltages;

FIG. 3 is a schematic diagram providing an exemplary illustration of asupply voltage circuit in the ET circuit of FIG. 1 configured accordingto an embodiment of the present disclosure to generate a number ofconstant voltages;

FIG. 4A is a schematic diagram of an exemplary ET voltage circuit, whichcan be configured according to one embodiment of the present disclosureto function as an ET voltage circuit in the ET circuit of FIG. 1 togenerate a number of ET modulated voltages based on the ET targetvoltages of FIG. 2 and the constant voltages of FIG. 3;

FIG. 4B is a schematic diagram of an exemplary ET voltage circuit, whichcan be configured according to another embodiment of the presentdisclosure to function as an ET voltage circuit in the ET circuit ofFIG. 1 to generate a number of ET modulated voltages based on the ETtarget voltages of FIG. 2 and the constant voltages of FIG. 3; and

FIG. 4C is a schematic diagram of an exemplary ET voltage circuit, whichcan be configured according to another embodiment of the presentdisclosure to function as an ET voltage circuit in the ET circuit ofFIG. 1 to generate a number of ET modulated voltages based on the ETtarget voltages of FIG. 2 and the constant voltages of FIG. 3.

DETAILED DESCRIPTION

The embodiments set forth below represent the necessary information toenable those skilled in the art to practice the embodiments andillustrate the best mode of practicing the embodiments. Upon reading thefollowing description in light of the accompanying drawing figures,those skilled in the art will understand the concepts of the disclosureand will recognize applications of these concepts not particularlyaddressed herein. It should be understood that these concepts andapplications fall within the scope of the disclosure and theaccompanying claims.

It will be understood that, although the terms first, second, etc. maybe used herein to describe various elements, these elements should notbe limited by these terms. These terms are only used to distinguish oneelement from another. For example, a first element could be termed asecond element, and, similarly, a second element could be termed a firstelement, without departing from the scope of the present disclosure. Asused herein, the term “and/or” includes any and all combinations of oneor more of the associated listed items.

It will be understood that when an element such as a layer, region, orsubstrate is referred to as being “on” or extending “onto” anotherelement, it can be directly on or extend directly onto the other elementor intervening elements may also be present. In contrast, when anelement is referred to as being “directly on” or extending “directlyonto” another element, there are no intervening elements present.Likewise, it will be understood that when an element such as a layer,region, or substrate is referred to as being “over” or extending “over”another element, it can be directly over or extend directly over theother element or intervening elements may also be present. In contrast,when an element is referred to as being “directly over” or extending“directly over” another element, there are no intervening elementspresent. It will also be understood that when an element is referred toas being “connected” or “coupled” to another element, it can be directlyconnected or coupled to the other element or intervening elements may bepresent. In contrast, when an element is referred to as being “directlyconnected” or “directly coupled” to another element, there are nointervening elements present.

Relative terms such as “below” or “above” or “upper” or “lower” or“horizontal” or “vertical” may be used herein to describe a relationshipof one element, layer, or region to another element, layer, or region asillustrated in the Figures. It will be understood that these terms andthose discussed above are intended to encompass different orientationsof the device in addition to the orientation depicted in the Figures.

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting of the disclosure.As used herein, the singular forms “a,” “an,” and “the” are intended toinclude the plural forms as well, unless the context clearly indicatesotherwise. It will be further understood that the terms “comprises,”“comprising,” “includes,” and/or “including” when used herein specifythe presence of stated features, integers, steps, operations, elements,and/or components, but do not preclude the presence or addition of oneor more other features, integers, steps, operations, elements,components, and/or groups thereof.

Unless otherwise defined, all terms (including technical and scientificterms) used herein have the same meaning as commonly understood by oneof ordinary skill in the art to which this disclosure belongs. It willbe further understood that terms used herein should be interpreted ashaving a meaning that is consistent with their meaning in the context ofthis specification and the relevant art and will not be interpreted inan idealized or overly formal sense unless expressly so defined herein.

Embodiments of the disclosure relate to an envelope tracking (ET)circuit and related power amplifier apparatus. In one aspect, an ETpower amplifier apparatus includes an ET circuit and a number ofamplifier circuits. The ET circuit is configured to provide a number ofET modulated voltages to the amplifier circuits for amplifyingconcurrently a number of radio frequency (RF) signals to respectivepower levels. In another aspect, the ET circuit is configured to includea target voltage circuit, a supply voltage circuit, and an ET voltagecircuit. The target voltage circuit is configured to generate a numberof ET target voltages adapted to the respective power levels of the RFsignals and/or respective impedances seen by the amplifier circuits. Thesupply voltage circuit is configured to generate a number of constantvoltages. The ET voltage circuit is configured to generate the ETmodulated voltages based on the ET target voltages and a selected one ofthe constant voltages. As such, it may be possible to adapt the ETmodulated voltages to the respective power levels of the RF signalsand/or respective impedances seen by the amplifier circuits, thushelping to improve linearity and efficiency of the amplifier circuits.Further, by providing the ET modulated voltages from a single ETcircuit, it may be possible to reduce a footprint and improve heatdissipation of the ET power amplifier apparatus.

In this regard, FIG. 1 is a schematic diagram of an exemplary ET poweramplifier apparatus 10 configured according to an embodiment of thepresent disclosure to support a number of amplifier circuits 12(1)-12(N)based on an ET circuit 14. The amplifier circuits 12(1)-12(N) may beconfigured to amplify a number of RF signals 16(1)-16(N) from inputpowers P_(IN-1)-P_(IN-N) to output powers P_(OUT-1)-P_(OUT-N),respectively. In a non-limiting example, the amplifier circuits12(1)-12(N) are coupled to a signal processing circuit 18. The signalprocessing circuit 18 may be configured to receive a digital signal 20,which may include a digital in-phase (I) signal 20I and a digitalquadrature (Q) signal 20Q. Accordingly, the digital signal 20corresponds to a time-variant signal envelope √{square root over(I²+Q²)}, wherein I and Q represent time-variant in-phase amplitude andquadrature amplitude of the digital signal 20, respectively.

The signal processing circuit 18 is configured to convert the digitalsignal 20 into the RF signals 16(1)-16(N). More specifically, the signalprocessing circuit 18 may be configured to pre-process the RF signal16(1)-16(N) to the input powers P_(IN-1)-P_(IN-N) and/or phase anglesθ₁-θ_(N), respectively, such that the RF signals 16(1)-16(N) can betransmitted coherently via RF beamforming.

The ET circuit 14 is configured to generate and provide a number of ETmodulated voltages V_(CC-1)-V_(CC-N) to the amplifier circuits12(1)-12(N), respectively. In examples discussed herein, the ETmodulated voltages V_(CC-1)-V_(CC-N) may be generated in accordance tothe input powers P_(IN-1)-P_(IN-N) of the RF signals 16(1)-16(N) and/orload impedances Z_(LOAD-1)-Z_(LOAD-N) as seen from the amplifiercircuits 12(1)-12(N) into the ET circuit 14. As such, it may be possibleto improve linearity and efficiency of the amplifier circuits12(1)-12(N). Further, by employing only the ET circuit 14 for generatingthe ET modulated voltages V_(CC-1)-V_(CC-N), as opposed to employingmultiple ET circuits, it may be possible to reduce footprint and heatdissipation in the ET power amplifier apparatus 10.

The ET circuit includes a target voltage circuit 22, a supply voltagecircuit 24, and an ET voltage circuit 26. The target voltage circuit 22is configured to receive a reference target voltage V_(TARGET) andgenerate a number of ET target voltages V_(TARGET-1)-V_(TARGET-N) basedon the reference target voltage V_(TARGET). The target voltage circuit22 will be further discussed in detail in reference to FIG. 2 below.

The supply voltage circuit 24 is configured to generate a number ofconstant voltages V_(DC1)-V_(DC-M). The supply voltage circuit 24 willbe further discussed in detail in reference to FIG. 3 below.

The ET voltage circuit 26 is coupled to the target voltage circuit 22and the supply voltage circuit 24. The ET voltage circuit 26 isconfigured to receive the ET target voltages V_(TARGET-1)-V_(TARGET-N)from the target voltage circuit 22 and the constant voltagesV_(DC-1)-V_(DC-N) from the supply voltage circuit 24. As discussed indetail in FIGS. 4A-4C, the ET voltage circuit 26 can be configuredaccording to various embodiments of the present disclosure to generatethe ET modulated voltages V_(CC-1)-V_(CC-N) based on the ET targetvoltages V_(TARGET-1)-V_(TARGET-N) and a selected constant voltage amongthe constant voltages V_(DC-1)-V_(DC-N).

FIG. 2 is a schematic diagram providing an exemplary illustration of thetarget voltage circuit 22 of FIG. 1 configured according to anembodiment of the present disclosure to generate the ET target voltagesV_(TARGET-1)-V_(TARGET-N). Common elements between FIGS. 1 and 2 areshown therein with common element numbers and will not be re-describedherein.

The target voltage circuit 22 may be coupled to a voltage processingcircuit 28, which is further coupled to the signal processing circuit18. In this regard, the voltage processing circuit 28 receives thedigital signal 20 that corresponds to the time-variant amplitudeenvelope √{square root over (I²+Q²)}. The voltage processing circuit 28includes an ET look-up table (LUT) 30 configured to store predeterminedcorrelations between the time-variant amplitude envelope √{square rootover (I²+Q²)} and a time-variant voltage envelope 32 associated with adigital target voltage signal 34. The voltage processing circuit 28 mayinclude a digital-to-analog converter (DAC) 36 for converting thedigital target voltage signal 34 into the reference target voltageV_(TARGET), which corresponds to a time-variant target voltage envelope38 that tracks (e.g., rises and falls) the time-variant voltage envelope32 as well as the time-variant amplitude envelope √{square root over(I²+Q²)}. In this regard, the reference target voltage V_(TARGET)corresponds to a dynamic voltage range defined by a maximum level targetvoltage V_(MAX-TARGET) and a minimum level target voltage V_(MIN-TARGET)(dynamic voltage range=V_(MAX-TARGET)−V_(MIN-TARGET)) of thetime-variant voltage envelope 32.

In a non-limiting example, the reference target voltage V_(TARGET) canbe a differential voltage signal. As such, the target voltage circuit 22may include a voltage converter 40 for converting the differentialtarget voltage signal to the reference target voltage V_(TARGET). Thetarget voltage circuit 22 may also include an anti-alias filter (AAF) 42for aliasing the reference target voltage V_(TARGET).

The target voltage circuit 22 includes a first offset converter 44configured to convert the reference target voltage V_(TARGET) to abaseline reference voltage V′_(TARGET) (e.g., 0 V) corresponding to thedynamic voltage range (V_(MAX-TARGET)−V_(MIN-TARGET)). The targetvoltage circuit 22 includes a number of multipliers 46(1)-46(N) coupledin parallel to the first offset converter 44 to receive the baselinereference voltage V′_(TARGET). The multipliers 46(1)-46(N) can beconfigured to multiply a dynamic voltage range with a number of slopefactors S₁-S_(N) to generate the ET target voltagesV_(TARGET-1)-V_(TARGET-N), respectively. In a non-limiting example, theslope factors S₁-S_(N) can be determined based on the equation (Eq. 1)below.S _(i)=(V _(MAX-TARGET-i) −V _(MIN-TARGET-i))/(V _(MAX-TARGET) −V_(MIN-TARGET))(1≤i≤N)  (Eq. 1)

In the equation above, V_(MAX-TARGET-i) and V_(MIN-TARGET-i) represent amaximum level and a minimum level of the ET target voltage V_(TARGET-i)(1≤i≤N) as defined in the ET LUT 30, respectively.(V_(MAX-TARGET)−V_(MIN-TARGET)) represents the dynamic voltage range ofthe reference target voltage V_(TARGET). The target voltage circuit 22includes a number of second offset converters 48(1)-48(N) coupled to themultipliers 46(1)-46(N), respectively. The second offset converters48(1)-48(N) are configured to adjust the ET target voltagesV_(TARGET-1)-V_(TARGET-N) based on a number of offset factors f₁-f_(N),respectively. In this regard, each of the ET target voltagesV_(TARGET-1)-V_(TARGET-N) may be generated based on the equation (Eq. 2)below.V _(TARGET-i) =S _(i)*(V _(MAX-TARGET) −V _(MIN-TARGET))+f_(i)(1≤i≤N)  (Eq. 2)

FIG. 3 is a schematic diagram providing an exemplary illustration of thesupply voltage circuit 24 of FIG. 1 configured according to anembodiment of the present disclosure to generate the constant voltagesV_(DC-1)-V_(Dc-M). Common elements between FIGS. 1 and 3 are showntherein with common element numbers and will not be re-described herein.

The supply voltage circuit 24 includes an inductor-based voltage circuit50 (denoted as “μLBB”), which is configured to generate a direct current(DC) voltage V_(DC) based on a battery voltage V_(BAT). Theinductor-based voltage circuit 50 is coupled to an inductor 52, which isconfigured to induce a DC current I_(DC) based on the DC voltage V_(DC).In a non-limiting example, the inductor-based voltage circuit 50 can bea buck-boost circuit configured to operate in a buck mode to generatethe DC voltage V_(DC) as being less than or equal to the battery voltageV_(BAT) or in a boost mode to generate the DC voltage V_(DC) as beinggreater than the battery voltage V_(BAT). In this regard, the supplyvoltage circuit 24 may include a controller 54, which can be a pulsewidth modulation (PWM) controller for example, configured to control theinductor-based voltage circuit 50. Specifically, the controller 54 maycontrol the inductor-based voltage circuit 50 to operate in the buckmode and the boost mode based on a first control signal 56 and a secondcontrol signal 58, respectively.

The inductor-based voltage circuit 50 is coupled to a capacitor-basedvoltage circuit 60 (denoted as “μCBB”). A capacitor 62 may be providedin between the inductor-based voltage circuit 50 and the capacitor-basedvoltage circuit 60. The capacitor 62 has one end coupled to a ground GNDand another end coupled in between the inductor-based voltage circuit 50and the capacitor-based voltage circuit 60.

The supply voltage circuit 24 includes a number of output ports64(1)-64(M) configured to output the constant voltagesV_(DC-1)-V_(DC-M), respectively. In one exemplary embodiment, a firstselected output port 64(M) is coupled to the inductor-based voltagecircuit 50 via a conductive line 66 directly. Accordingly, the firstselected output port 64(M) outputs the DC voltage V_(DC) as a firstselected constant voltage V_(DC-M) among the constant voltagesV_(DC-1)-V_(DC-M). According to the exemplary embodiment, one or moresecond selected output ports 64(1)-64(M−1) are coupled to thecapacitor-based voltage circuit 60. Accordingly, the second selectedoutput ports 64(1)-64(M−1) are configured to output one or more secondselected constant voltages V_(DC-1)-V_(DC-M-1), respectively.

In this regard, the capacitor-based voltage circuit 60 is configured togenerate the second selected constant voltages V_(DC-1)-V_(DC-M-1) basedon the DC voltage V_(DC). In a non-limiting example, the capacitor-basedvoltage circuit 60 can generate the second selected constant voltagesV_(DC-1)-V_(DC-M-1) by multiplying the DC voltage V_(DC) with one ormore predefined scaling factors f_(S-1)-f_(S-M-1), respectively. In thisregard, each of the second selected constant voltagesV_(DC-1)-V_(DC-M-1) can be determined based on the equation (Eq. 3)below.V _(DC-i) =V _(DC) *f _(S-i)(1≤i≤M−1)  (Eq. 3)

In one embodiment, each of the predefined scaling factorsf_(S-1)-f_(S-M-1) can be a fractional scaling factor lesser than one(1). In this regard, each of the second selected constant voltagesV_(DC-1)-V_(DC-M-1) is lesser than the first selected constant voltageV_(DC-M). Accordingly, the capacitor-based voltage circuit 60 can beconfigured to operate exclusively in the buck mode. In a non-limitingexample, the constant voltages V_(DC-1)-V_(DC-M) can be outputted fromthe output ports 64(1)-64(M) based on ascending voltage values(V_(DC-1)≤V_(DC-2)≤ . . . ≤V_(DC-M-1)≤V_(DC-M)).

In one embodiment, each of the predefined scaling factorsf_(S-1)-f_(S-M-1) can be greater than 1. In this regard, each of thesecond selected constant voltages V_(DC-1)-V_(DC-M-1) is greater thanthe first selected constant voltage V_(DC-M). Accordingly, thecapacitor-based voltage circuit 60 can be configured to operateexclusively in the boost mode.

In one embodiment, each of the predefined scaling factorsf_(S-1)-f_(S-M-1) can be either greater than 1 or lesser than 1. In thisregard, each of the second selected constant voltagesV_(DC-1)-V_(DC-M-1) can be greater than the first selected constantvoltage V_(DC-M) or lesser than the first selected constant voltageV_(DC-M). Accordingly, the capacitor-based voltage circuit 60 can beconfigured to operate in both the buck mode and the boost mode(buck-boost mode).

The supply voltage circuit 24 includes a voltage feedback line 68coupled from one of the second selected output ports 64(1)-64(M−1) tothe controller 54. The voltage feedback line 68 is configured to carry avoltage feedback signal 70 indicative of a preselected constant voltageamong the second selected constant voltages V_(DC-1)-V_(DC-M-1). In anon-limiting example, the voltage feedback line 68 can be coupled fromthe output port 64(1) to the controller 54. The voltage feedback line 68is configured to carry the voltage feedback signal 70 indicative of thepreselected constant voltage V_(DC-1). Since all of the second selectedconstant voltages V_(DC-1)-V_(DC-M) are related to the DC voltageV_(DC), the voltage feedback signal 70 can be used to further indicateall of the second selected constant voltages V_(DC-1)-V_(DC-M).Accordingly, the controller 54 may control the inductor-based voltagecircuit 50 to adjust the DC voltage V_(DC) based on the voltage feedbacksignal 70.

The supply voltage circuit may include a clock generator 72 configuredto generate an operating clock 74 for the capacitor-based voltagecircuit 60. In a non-limiting example, the clock generator 72 cangenerate the operating clock 74 based on a reference clock CLK that isalso configured to operate the controller 54.

FIG. 4A is a schematic diagram of an exemplary ET voltage circuit 26A,which can be configured according to one embodiment of the presentdisclosure to function as the ET voltage circuit 26 in the ET circuit 14of FIG. 1 to generate the ET modulated voltages V_(CC-1)-V_(CC-N) basedon the ET target voltages V_(TARGET-1)-V_(TARGET-N) of FIG. 2 and theconstant voltages V_(CC-1)-V_(DC-M) of FIG. 3. Common elements betweenFIGS. 1 and 4A are shown therein with common element numbers and willnot be re-described herein.

The ET voltage circuit 26A includes a number of voltage controllers76(1)-76(N) coupled to a number of voltage selection circuits78(1)-78(N), respectively. Each of the voltage controllers 76(1)-76(N)can be a microcontroller or a field programmable gate array (FPGA), forexample. Each of the voltage selection circuits 78(1)-78(N) isconfigured to receive the constant voltages V_(DC-1)-V_(DC-M) from thesupply voltage circuit 24. In a non-limiting example, the voltageselection circuits 78(1)-78(N) can be configured to include a number ofswitching circuits 80(1)-80(N). Each of the switching circuits80(1)-80(N) can be controlled by a respective voltage controller tooutput a selected constant voltage among the constant voltagesV_(DC-1)-V_(DC-M) as a respective ET modulated voltage among the ETmodulated voltages V_(CC-1)-V_(CC-N). For example, the voltagecontroller 76(1) can control the switching circuit 80(1) in the voltageselection circuit 78(1) to output a selected one of the constantvoltages V_(DC-1)-V_(DC-M) as the ET modulated voltage V_(CC-1). In thisregard, the voltage selection circuits 78(1)-78(N) collectively output anumber of selected constant voltages as the ET modulated voltagesV_(CC-1)-V_(CC-N), respectively.

Each of the voltage controllers 76(1)-76(N) can be configured todetermine a selected constant voltage V_(DC-S) among the constantvoltages V_(DC-1)-V_(DC-M) for a respective voltage selection circuitamong the voltage selection circuits 78(1)-78(N) based on the equation(Eq. 4) below.V _(DC-S)=minimize[V _(DC-j)≥(V _(TARGET-i) +V_(Headroom))](1≤i≤N)(1≤j≤M)  (Eq. 4)

In the equation above, V_(DC-j) represents any of the constant voltagesV_(DC-1)-V_(DC-M), V_(TARGET-i) represents a respective ET targetvoltage among the ET target voltages V_(TARGET-1)-V_(TARGET-N), andV_(Headroom) represents a predefined headroom voltage (e.g., 0.9 V). Inthis regard, each of the voltage controllers 76(1)-76(N) can beconfigured to control the respective voltage selection circuit to outputthe selected constant voltage as being a smallest constant voltage amongthe constant voltages V_(DC-1)-V_(DC)-M that is greater than or equal tothe respective ET target voltage among the ET target voltagesV_(TARGET-1)-V_(TARGET-N). For example, the voltage controller 76(1) cancontrol the voltage selection circuit 78(1) to output the smallestconstant voltage among the constant voltages V_(DC-1)-V_(DC-M) that isgreater than or equal to the ET voltage V_(TARGET-1) as the ET modulatedvoltage V_(CC-1). Notably, the ET voltage circuit 26A is configured togenerate the ET modulated voltages V_(CC-1)-V_(CC-N) corresponding to anumber of non-continuous voltage envelopes 82(1)-82(N), respectively.

FIG. 4B is a schematic diagram of an exemplary ET voltage circuit 26B,which can be configured according to one embodiment of the presentdisclosure to function as the ET voltage circuit 26 in the ET circuit 14of FIG. 1 to generate the ET modulated voltages V_(CC-1)-V_(CC-N) basedon the ET target voltages V_(TARGET-1)-V_(TARGET-N) of FIG. 2 and theconstant voltages V_(DC-1)-V_(DC-M) of FIG. 3. Common elements betweenFIGS. 1 and 4B are shown therein with common element numbers and willnot be re-described herein.

The ET voltage circuit 26B includes a number of voltage controllers84(1)-84(N) coupled to a number of voltage selection circuits86(1)-86(N), respectively. Each of the voltage controllers 84(1)-84(N)can be a microcontroller or a field programmable gate array (FPGA), forexample. The ET voltage circuit 26B includes a number of voltageamplifiers 88(1)-88(N) configured to output the ET modulated voltagesV_(CC-1)-V_(CC-N) based on the ET target voltagesV_(TARGET-1)-V_(TARGET-N) and a number of supply voltagesV_(SUP-1)-V_(SUP-N).

Each of the voltage selection circuits 86(1)-86(N) includes a number offield-effect transistors (FETs) 90(1)-90(M) provided in a serialarrangement. The FETs 90(1)-90(M) in each of the voltage selectioncircuits 86(1)-86(N) include a number of gate electrodes 92(1)-92(M)coupled to a respective voltage controller among the voltage controllers84(1)-84(N). The FETs 90(1)-90(M) in each of the voltage selectioncircuits 86(1)-86(N) include a number of drain electrodes 94(1)-94(M)coupled to the supply voltage circuit 24 to receive the constantvoltages V_(DC-1)-V_(DC-M), respectively. The FETs 90(1)-90(M) in eachof the voltage selection circuits 86(1)-86(N) include a number of sourceelectrodes 96(1)-96(M) coupled to a respective voltage amplifier amongthe voltage amplifiers 88(1)-88(N) to provide a respective supplyvoltage among the supply voltages V_(SUP-1)-V_(SUP-N). The ET voltagecircuit 26B includes a number of second FETs 98(1)-98(N) coupledrespectively between the voltage selection circuits 86(1)-86(N) and theground GND.

Each of the voltage controllers 84(1)-84(N) is configured to control arespective voltage selection circuit among the voltage selectioncircuits 86(1)-86(N) to output a selected constant voltage among theconstant voltages V_(DC-1)-V_(DC-M) to a respective voltage amplifieramong the voltage amplifiers 88(1)-88(N) as a respective supply voltageamong the supply voltages V_(SUP-1)-V_(SUP-N). For example, the voltagecontroller 84(1) is configured to control the voltage selection circuit86(1) to output any of the constant voltages V_(DC-1)-V_(DC-M) to thevoltage amplifier 88(1) as the supply voltage V_(SUP-1). In this regard,the voltage selection circuits 86(1)-86(N) collectively output a numberof selected constant voltages as the supply voltagesV_(SUP-1)-V_(SUP-N), respectively. Each of the voltage controllers84(1)-84(N) may determine the respective constant voltage to beoutputted from the respective voltage selection circuit based on theequation (Eq. 4) above.

By determining the supply voltages V_(SUP-1)-V_(SUP-N) based on the ETtarget voltages V_(TARGET-1)-V_(TARGET-N), it may be possible to causethe voltage amplifiers 88(1)-88(N) to operate with improved efficiency.Notably, the ET voltage circuit 26B is configured to generate the ETmodulated voltages V_(CC-1)-V_(CC-N) corresponding to a number ofcontinuous voltage envelopes 100(1)-100(N), respectively.

FIG. 4C is a schematic diagram of an exemplary ET voltage circuit 26C,which can be configured according to one embodiment of the presentdisclosure to function as the ET voltage circuit 26 in the ET circuit 14of FIG. 1 to generate the ET modulated voltages V_(CC-1)-V_(CC-N) basedon the ET target voltages V_(TARGET-1)-V_(TARGET-N) of FIG. 2 and theconstant voltages V_(DC-1)-V_(DC-M) of FIG. 3. Common elements betweenFIGS. 1, 4B, and 4C are shown therein with common element numbers andwill not be re-described herein.

The ET voltage circuit 26C further includes a number of linear FETs102(1)-102(N), which can be p-type FETs (PFETs) for example. The linearFETs 102(1)-102(N) include a number of gate terminals 104(1)-104(N)coupled to the voltage amplifiers 88(1)-88(N), respectively. The linearFETs 102(1)-102(N) include a number of source terminals 106(1)-106(N)coupled to the voltage selection circuits 86(1)-86(N), respectively. Thelinear FETs 102(1)-102(N) include a number of drain terminals108(1)-108(N) coupled to the second FETs 98(1)-98(N), respectively. Thelinear FETs 102(1)-102(N) are configured to output the ET modulatedvoltages V_(CC-1)-V_(CC-N) respectively from the drain terminals108(1)-108(N) with improved linearity.

Those skilled in the art will recognize improvements and modificationsto the preferred embodiments of the present disclosure. All suchimprovements and modifications are considered within the scope of theconcepts disclosed herein and the claims that follow.

What is claimed is:
 1. An envelope tracking (ET) voltage circuitcomprising: a plurality of voltage selection circuits each configured toreceive a plurality of constant voltages; and a plurality of voltagecontrollers coupled to the plurality of voltage selection circuits,respectively, and configured to: receive a plurality of ET targetvoltages, respectively; control the plurality of voltage selectioncircuits to output a plurality of selected constant voltages based onthe plurality of ET target voltages, respectively; and cause a pluralityof ET modulated voltages to be generated based on the plurality of ETtarget voltages and the plurality of selected constant voltages,respectively.
 2. The ET voltage circuit of claim 1 wherein: theplurality of voltage selection circuits comprises a plurality ofswitching circuits each configured to receive the plurality of selectedconstant voltages; and the plurality of voltage controllers coupled tothe plurality of switching circuits, respectively, the plurality ofvoltage controllers each configured to: determine a respective selectedconstant voltage to be outputted by a respective switching circuit amongthe plurality of switching circuits based on a respective ET targetvoltage among the plurality of ET target voltages; and control therespective switching circuit to output the respective selected constantvoltage as a respective ET modulated voltage among the plurality of ETmodulated voltages.
 3. The ET voltage circuit of claim 2 wherein each ofthe plurality of voltage controllers is further configured to determinethe respective selected constant voltage as being equal to minimize[V_(DC-j)≥(V_(TARGET-i)+V_(Headroom))] (1≤i≤N) (1≤j≤M), wherein:V_(DC-j) represents any of the plurality of constant voltages;V_(TARGET-i) represents the respective ET target voltage among theplurality of ET target voltages; V_(Headroom) represents a predefinedheadroom voltage; i represents any one of the plurality of ET targetvoltages; N represents a count of the plurality of ET target voltages; jrepresents any one of the plurality of constant voltages; and Mrepresents a count of the plurality of constant voltages.
 4. The ETvoltage circuit of claim 1 further comprising a plurality of voltageamplifiers coupled to the plurality of voltage controllers and theplurality of voltage selection circuits, respectively, the plurality ofvoltage amplifiers is configured to generate the plurality of ETmodulated voltages based on the plurality of ET target voltages and aplurality of supply voltages, respectively.
 5. The ET voltage circuit ofclaim 4 wherein each of the plurality of voltage controllers is furtherconfigured to: determine a respective selected constant voltage to beoutputted by a respective voltage selecting circuit among the pluralityof voltage selection circuits based on a respective ET target voltageamong the plurality of ET target voltages; and control the respectivevoltage selection circuit to output the respective selected constantvoltage to a respective voltage amplifier among the plurality of voltageamplifiers as a respective supply voltage among the plurality of supplyvoltages.
 6. The ET voltage circuit of claim 5 wherein the plurality ofvoltage selection circuits each comprises a plurality of field-effecttransistors (FETs) disposed according to a serial arrangement, theplurality of FETs comprising: a plurality of drain electrodes configuredto receive the plurality of constant voltages, respectively; a pluralityof gate electrodes coupled to a respective voltage controller among theplurality of voltage controllers; and a plurality of source electrodescoupled to a respective second FET among a plurality of second FETs. 7.The ET voltage circuit of claim 6 wherein the ET voltage circuit furthercomprises a plurality of linear FETs, each of the plurality of linearFETs comprising: a gate terminal coupled to a respective voltageamplifier among the plurality of voltage amplifiers; a source terminalcoupled to a respective voltage selection circuit among the plurality ofvoltage selection circuits; and a drain terminal coupled to a respectivesecond FET among the plurality of second FETs and configured to output arespective ET modulated voltage among the plurality of ET modulatedvoltages.